FIGS. 5 and 6 illustrate a known inflator 500 for inflating an inflatable vehicle occupant protection device. The inflator 500 include includes a container 502 that is formed from a cylindrical member 504, a diffuser endcap 506, and an igniter endcap 508. A chamber 510 is defined in the container 502. A gaseous propellant 512 is stored in the chamber 510. The gaseous propellant 512 is ignitable for providing inflation fluid.
A flow opening 518 extends through the diffuser endcap 506. A rupturable burst disk 520 closes the flow opening 518 for maintaining the gaseous propellant 512 in the chamber 510.
A through-hole 524 extends through the igniter endcap 508. The through-hole 524 narrows slightly at an end adjacent the chamber 510. A rupturable burst disk 526 closes an opening of the through-hole 524 adjacent the chamber 510.
An igniter 530 is secured to the igniter endcap 508. The igniter 530 is actuatable for providing combustion products for igniting the gaseous propellant 512 in the chamber 510.
FIG. 6 illustrates the inflator 500 in an actuated condition. When the igniter 530 is actuated, combustion products generated from ignition of the igniter 530 fill the through-hole 524 of the igniter endcap 508 and rupture the burst disk 526. When the burst disk 526 ruptures, the combustion products flow from the through-hole 524 into the chamber 510. When the combustion products enter the chamber 524, the combustion products are at a pressure that is higher than the pressure of the gaseous propellant 512 within the chamber 510. As a result, upon entering the chamber 510, the combustion products fan outwardly in a radial direction relative to a central axis of the through-hole 524. The outward fanning of the combustion products results in a generally conical flow pattern for the combustion products, as is illustrated at 534 in FIG. 6.
When the flow opening 518 for inflation fluid is located on an opposite end of the container 502 from the igniter 530, as is illustrated in FIGS. 5 and 6, the outward fanning of the combustion products results in a burn zone that is located adjacent the igniter endcap 508 and away from the flow opening 518. As a result, when the burst disk 520 covering the flow opening 518 is ruptured, some of the gaseous propellant 512 may exit the chamber 510 through the flow opening without being combusted.
To help minimize the amount of uncombusted gaseous propellant 512 exiting the chamber 510 through the flow opening 518, a high burn efficiency is desired. A higher burn efficiency may be achieved by locating the burn zone closer to the flow opening.